Rwanda's deadly methane lake becomes source of future power

May 25, 2014
by Stephanie Aglietti

A man looks towards the hills of Rwanda on the eastern edge of Lake Kivu from the Democratic Republic of the Congo's eastern city of Goma on May 28, 2012

Beneath the calm waters of Lake Kivu lie vast but deadly reserves of methane and carbon dioxide, which Rwanda is tapping both to save lives and provide a lucrative power source.

Plans are in place to pump out enough gas for power that would nearly double Rwanda's current electricity capacity, as well as reducing the chance of what experts warn could be a potentially "catastrophic" natural disaster.

The glittering waters of the inland sea, which straddles the border of Rwanda and the Democratic Republic of Congo, contain a dangerous and potent mix of the dissolved gases that if disturbed would create a rare "limnic eruption" or "lake overturn", expert Matthew Yalire said.

Levels of carbon dioxide (Co2) and methane are large and dangerous enough to risk a sudden release that could cause a disastrous explosion, after which waves of Co2 would suffocate people and livestock around, explained Yalire, a researcher at the Goma Volcano Observatory, on the lake's DR Congo shore.

"Right now the lake is stable, but for how long?" asked Yalire, who believes that extracting potentially explosive methane is one way to help "stabilise" the lake.

Near the town of Rubavu, a pilot project of the Rwandan government is already producing about two megawatts of electricity from the methane in the lake.

But a new, additional plant is being built on Kivu's eastern shore, where the US-based power company ContourGlobal plans massively to boost production.

"Our team is focused on extracting methane from the lake to generate electricity that will expand household access to power, lower costs, and reduce environmental hazards," ContourGlobal said.

Its 200 million dollar (145 million euro) "KivuWatt" project aims to lessen the natural threat of an explosion, while turning the deadly gas into a source of energy and profit.

Two million people at risk

On the lake's Rwandan shoreline and at the foot of green hills dotted with banana plantations, hundreds of construction workers are building a platform due to be installed on the lake by the end of the year.

Rather than being a drill platform, it will instead suck up the methane trapped in the depths.

A man fishes on the edge of Lake Kivu on May 28, 2012 near the city of Goma in North Kivu province in the Democratic Republic of the Congo

"There is no drilling, gas is pumped from the lower layers of the lake that are saturated with methane," the KivuWatt project's chief, Yann Beutler, told AFP.

"From the moment when the water rises to the surface, it releases gases that are collected."

The methane and Co2 are separated, with the methane sent to a plant on the shore and the Co2 re-dissolved and returned to the depths of the lake.

"The structure of the lake, and the flora and fauna, are not changed," Beutler added.

The project's first phase is planned to generate over 25 megawatts of energy, with production to be multiplied four times in the second phase to 100 MW, almost doubling Rwanda's current national production capacity of about 115 MW.

The scheme is largely financed by private capital, though some 45 percent of the funding takes the shape of loans from international development institutions.

ContourGlobal has signed a 25-year concession with the Rwandan government and an agreement with the country's national power producer and distributor.

Lessons from Cameroon

The electrification of Rwanda is a top objective of Kigali's government, which aims to more than triple access to electricity from a mere 18 percent of the population today to 70 percent by 2017.

The methane will also help Rwanda fulfil the further goal of diversifying energy sources.

A view from a UN base on the edge of Lake Kivu in the Democratic Republic of the Congo's eastern city of Goma on May 28, 2012 shows the hills of Rwanda in the background

Today, almost half of its energy comes from fossil fuels, with the annual bill for imported fuel topping some 40 million dollars (30 million euros).

Kivu is not unique: two other lakes in Cameroon—Monoun and Nyos—have similar high concentrations of the gases. In 1984, a limnic eruption killed 37 people around Lake Monoun, then in 1986 a similar disaster at Lake Nyos claimed more than 1,700 lives. These tragedies have been seen as dire warnings for people near Lake Kivu.

"It is essential to extract the gas from the lake," said Martin Schmid, a researcher at the Swiss Federal Institute of Aquatic Science and Technology (Eawag).

"If we let the gases accumulate for a long time, we should expect at a catastrophic eruption of gas."

With some two million people living close to the lake shore in both Rwanda and DR Congo, any eruption could be disastrous.

An active nearby volcano, Mount Nyiragongo, which smothered part of the Kivu lakeshore city of Goma with lava in 2002, highlights the real risk that geological activity in the lake could trigger an explosion.

Both the lake and volcano are located on Africa's continental Rift zone, where the Earth's tectonic plates are very slowly being pulled apart.

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The methane is taken out the CO2 is redissolved and send back to the bottom.Does not that mean that the CO2 threat remains?

The CO2 is probably injected at much lesser depth, where it increases acidity in the short-term, but will ultimately be re-emitted into the atmosphere as temp/density gradients drive the dissolved gas out of solution.

You are right, though --it seems pretty idiotic to pump it back into the water, when it could be either directly vented to the atmosphere(where it would naturally end up anyway ie, it isn't anththropogenic CO2) or compressed and bottled as an industrial gas.

So, they will produce one source of revenue only, where two could be --and still manage to increase the environmental damage caused by lake water acidification, or possible dangerous buildup of CO2 sufficient to cause another suffocation event.

I think the person writing the article is basically ignorant of the siphoning process.

Totally fucking ignorant....

"Rather than being a drill platform, it will instead suck up the methane trapped in the depths."

Noooo it does not suck up the methane (idiot) once the water from the lowest depths of the lake, are sucked up to a shallow enough depth, the dissolved gasses come out of solution and start to everesce and fizz... and that volume of water, at that depth inside the pipe, is of a much lower density than the surrounding water, outside of the pipe - and the fizzy water races upwards towards the surface and it draws water from the bottom of the lake in behind it. It becomes a self sustaining process.

"There is no drilling, gas is pumped from the lower layers of the lake that are saturated with methane," the KivuWatt project's chief, Yann Beutler, told AFP."

There is NO pumping - only bigger or more piping to allow the process to raise more degassing water.

"From the moment when the water rises to the surface, it releases gases that are collected."

True.....

I hate GROSSLY inept, factually incorrect reporting....

"The methane and Co2 are separated, with the methane sent to a plant on the shore and the Co2 re-dissolved and returned to the depths of the lake."

At best the CO2 would be simply piped to the burner along with the methane - because it's easy... that or it's just vented or used in some industrial process or farming etc..

But pumping it back to the bottom of the lake to add to the dilution of methane and keep adding to the risk of the lake belching a massive ground hugging cloud of smothering gas - for some 2 million surrounding people - not fucking likely.

If you sift through the links or subjects and locations and events - there is a ton of really good information on this subject.

The gist of it is that these volcanic lakes are really deep -and the volcanic bits, percolate CO2 and other gases into the lake, and in some places, where there is enough dead things landing on the bottom, methane is created too.

But the lakes are soooooo deep that the pressure in the lower depths, is high enough to dissolve enormous amounts of gas into solution - like a carbonated beverage, while the upper layers of water are largely gas free - the layers are stratified.

It only takes enough dissolved gas, or an internal land slip / rock fall inside the lake, to create a penetration of the stratified layering, that opens a pathway up to the surface for the saturated bottom layers to rise.

As the bottom water rises, the gas comes out of solution and it expands like a shaken carbonated beverage, which rapidly lowers it's density - and -

The madly gassing bottom water races towards the surface pulling the water from the bottom up with it and this too gives up it's dissolved gasses as it rises...

It's a chain reaction - exactly like a Mentos mint, dropped into a bottle of coke.

Only there are HUGE volumes of water - as in LOTS of cubic kilometers of it, with enormous amounts of dissolved CO2 - and the lakes essentially invert - all the bottom water surges to the top.

Assuming it's a nearly wind free night...... as has happened before.

CO2 is heavier than air, and it's COLD, and it forms an enormous smothering oxygen free blanket, that surges out of the crater and runs over the sides, and it especially concentrates in valleys as it rolls down hill.

The Lake Kivu - with it's super saturated solution of methane, CO2, and hydrogen sulphide etc., IF the entire lake inverted and degassed, the release of the enormous amounts of CO2 is one issue.

However the explosion hazard of 65 billion m3 of usable methane, which is lying dormant at the bottom of Lake Kivu, at a depth of 250 m, suddenly surging to the surface, is an absolute certainty - in an area where kerosene lanterns and cooking fires are in use all around the lake.

That is about 40 - 50 million tons of oil all going bang at the same moment....

In some HUGE partially mixed with the atmosphere style of cloud - more or less hugging the land surface to some considerable depth - before it goes bang.

LOL - mega-blast.

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